Metalsmith Carol Holaday wanted a safer way to etch and has been experimenting with electro-etching with salt water.  She shares her results, containers and equipment here:

http://carolholaday.wordpress.com/2013/02/14/electro-etching-continued

and here:

http://carolholaday.wordpress.com/2013/03/26/the-larger-etching-tank

The most comprehensive source on the web with free information on safer printmaking is Non-toxic Print, here’s the link to their extensive tutorial on electro-etching, which covers etching multiple types of metal:

http://www.nontoxicprint.com/electroetching.htm

And Carol has a virtual studio tour over on her main website!

http://carolholaday.com/htmlpages/studiotourpage.htm